This invention relates to a process for the biological treatment of waste water using microorganisms whose living conditions are maintained by the addition of oxygen into a contact path which is arranged at a slight upward angle towards the water surface and has an interior air-permeable and an exterior air-impermeable wall, whereby air and contaminated waste water are added into the contact path for the development of the microorganisms approximately parallel to the water surface. The invention also relates to a device for implementing the process which has an underwater support frame in which a double-walled duct is arranged with a slight rise towards the water surface and holds the air bubbles and which has installations which prevent the premature rise of the latter and which in its capacity as contact path holds the contaminated waste water which was added via an aerator and the air.
Such processes are used for the biological decontamination of waste waters and especially for the regeneration of waters which are seriously contaminated and silted because of a lack of oxygen. A known device used for this purpose (German Patent 2523591) has a water jet pump which is used to produce a water-air mixture which is then passed for a certain time period in a pipe in such a way that the air bubbles do not rise too fast. The pipe is extended so far and is equipped with an air-permeable interior wall and an air-impermeable exterior wall that the individual air bubbles which are as small as possible must travel long distances and are, during this time, in intensive contact with the water. In this way oxygen-saturated water is obtained in a certain area so that the bacteria eliminating the sludge are preserved or are able to multiply as quick as possible. The device stands with its support frame on the bottom of the water and may, if needed, be transported from one location to another. In order to ensure the necessary contact of the air bubbles with the water, such contact paths have a length of 15 m or more. Inside of the contact paths are installations at which the individual microorganisms may also settle and develop in order to ensure the shortest possible and complete purification of the water. But the disadvantage is that the microorganisms develop more or less randomly depending on oxygen and food supply, i.e. the added contaminations. In addition, the microorganisms which have just achieved optimum effectiveness are removed with the purified waste water, something which is partially desired, but which on the other hand constitutes an overall impediment of the even development of microorganisms. This causes problems particularly when the composition of the waste water changes. Then, either not enough microorganisms are present, or the present microorganisms cannot change, or the currently required microorganisms are available only in small or minute numbers. British application 587 400 publishes a process for waste water treatment in a contact path which is simply aerated cross-wise to flow direction. Part of the microorganisms leaving the contact path are recycled together with absorbed sludge into the contact path. Notwithstanding the fact that this achieves only an insufficient aeration, i.e. supply of oxygen, the suggestion of the recycling of sludge obviously shows that only a small purification result may be presupposed.